Crerating a new iSCSI storage domain with RHEV 3.2 and storage live migration

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Hello -

This makes me a little bit apprehensive. I have a RHEV VM filling up its virtual disk. The iSCSI storage domain where it lives is also filling up. The SAN has plenty of room, so I made another iSCSI volume and set up another iSCSI storage domain in my data center. This all went smoothly. With the new storage domain in place, I want to live migrate the storage for my full VM to this new storage domain. Then I'll create another virtual disk and move some of the data from the full disk to the new disk. The VM is running Windows Server 2008R2.

But now I'm afraid to pull the trigger. I have 2 hosts, named rheva and rhevb. Here's the sequence of events and why I am now afraid:

Add a new iSCSI storage domain - so now the datacenter has 2 storage domains.
Host rhevb is SPM and handles it. The process goes smoothly.
But host rheva declares itself non operational after it can't see the new storage domain.
The VM running on rheva live migrates to host rhevb.
I try to activate rheva - this fails with an error because it can't see the new iSCSI storage domain.
I put rheva into maintenance, then activate it.
This works.

OK, no disasters and no application downtime. And I think I know what's going on. Host rhevb had the SPM role and did the work, so it "knew" about the new iSCSI volume. But how to tell host rheva about the new storage? That was ugly. I have to put rheva into maintenance mode and take it out again so that RHEV-M can feed it the right commands to connect up to its new iSCSI world.

In my case, I got away with it because my surviving host has enough capacity to run all the VMs here. Barely.

What would happen if this were a large datacenter with lots of hosts? Would all the non SPM hosts have gone non-operational, unable to find this new storage? And would they all try cram their VMs onto a now overburdened SPM host?

So before I try a storage live migration on this company's email and application server, what is everyone else's experience with storage live migrations? The current virtual disk is thin provisioned - I would like to make it thick provisioned after migrating it.

thoughts?

thanks

  • Greg Scott
GS

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